The successful use of water treatment tanks requires not only proper water flow through the tank for treatment, but also proper reverse flow for backwashing, to obtain the best regeneration, air mixing, and separation of water treatment media. The backwashing step is conventionally used to clean the mineral of suspended solids and to loosen the bed for efficient regeneration of the ion exchange materials.
It is typical that the backwash and regeneration flow rates through a water treatment tank are substantially less than the maximum water flow rate through the tank when it is in service. Thus, tank inlet and outlet ports which are adapted for a normal service flow rate may exhibit flow disadvantages during the backwash step, in which flow through the inlet and outlet of the tank is typically reversed. For example, it is desired for the flow velocity of water coming into the tank during the backwash step to be above a certain minimum velocity, to cause separation by movement of the water treatment media in the tank. In the prior art, this is not easily done, while at the same time maintaining an adequate flow capacity through the inlet and outlet, to provide the desired maximum flow for the water treatment tank during its service cycle.
Also, as another issue, it is highly desirable for the water treatment media to remain trapped in the tank so that media particles do not flow out of the tank along with water passing therethrough.
By this invention, a flow collector/distributor is provided which addresses both of these needs. The flow collector/distributor of this invention is typically used as the flow outlet during normal operation but as the flow inlet during the backwash, while effectively limiting the migration of water treatment media from the tank. At the same time, the flow collector/distributor may provide an increased backwash flow velocity into the tank, even when the total flow volume of backwash solution is less than the normal flow. This is accomplished by the automatic reduction of the number of flow orifices in reverse flow, when compared with normal flow, for a consequent increase in the flow velocity of solution through the flow collector/distributor in reverse flow.
Also, a slot system in a housing for improved flow of water into or out of the housing is disclosed, where the presence of partially blocking granular media cannot seriously restrict the flow which passes through the slot system in a large plurality of different directions.